(1) Field of the Invention
The present invention relates to routing method and a relay node in a network. More particularly, the invention relates to a data transmission control and a relay node for routing a data packet by using information for data identification in an application layer of the data packet in order to efficiently transfer large data which is, for example, multimedia data such as video image and sound, and intra-enterprise technical data. In particular, the invention relates to data packet transmission control, packet routing with store-and-forward method, and a relay node using a storage address in a network constructed by storage units as components.
(2) Description of Related Art
In a conventional network system, routing technique according to a network layer protocol of the International Organization for Standardization/Open Systems Interconnection (ISO/OSI) reference model is used. Major protocols are the routing information protocol (RIP) of determining the most optimized route based on the number of routers existing on a route, the open shortest path first (OSPF) of determining a preferred route from a link state, and a border gateway protocol (BGP) of determining a preferred communication route between autonomous systems on the basis of properties of a link. According to the protocols, routers notify each other of routing information held in themselves, thereby propagating a network topology. By a calculating method determined for each protocol, on the basis of information such as address information defined in a network layer and the type of a communication line, a correspondence table (routing table) for indicating the relation between a destination of data and a destination interface is generated.
Each of data relay nodes (routers) forming a network generates, as a routing table, a table indicative of correspondence between a destination address and an output port on the basis of routing information learned from the other routers and connection information of itself and holds the table in a memory. Between the routers, routing information is periodically exchanged according to a routing protocol. The routing table is updated each time a link failure or a change in the network topology occurs.
On the routing table, one output port determined as the most appropriated output port is registered as an output port corresponding to one destination address. A data packet whose destination is determined by each router on the basis of the routing table is sent out to a relay node or terminal having the destination network address. An existing IP network is characterized in that only one route from a router to a destination is determined on the basis of a network address. In the case where traffic is heavy in a certain area, since a section of high load and a section which is not usually used are formed in the network, the network bandwidth cannot be effectively used as a whole.
A technique of performing high-speed secure transmission by adding a function to an IP network is being developed. Multi protocol label switching (MPLS) is a technique to which attention is paid most at present and being standardized in IETF and the like. The MPLS is a technique of realizing traffic control by performing a flow control using a label in transfer between routers. The MPLS is a means for establishing a path of connection type in a connectionless network and is highly effective from the viewpoint of security. In the MPLS, a route is set with reference to a routing table in the network layer, and a path is uniquely assured depending on the bandwidth usage by traffic engineering.
A protocol such as RSVP-TE or CR-LDP is standardized in IETF. A technique of setting a route capable of transferring data more efficiently depending on network usage on a reserved route when a route establishing request is sent from an MPLS network edge router on the user side to an edge router on the data transmission side is being studied. However, since a route and a label are determined in accordance with network conditions at the time point of the route setting, this technique does not adapt to a dynamic route control during data communication.
In a method called policy routing of setting an efficient route by centralizing the management of network usage, in response to information of congestion, a failure, or the like in a network bandwidth, each router can dynamically change the route on the basis of predetermined operation criteria or policy. In the routing selection, however, the number of available routes is limited. A network technique for distributing large data is as follows.
As data becomes larger and an enterprise information system expands, a system called a content distribution network (CDN) is in increasing demand. An object of the technique is to increase availability of data by improving a response to a request. Concretely, main subjects are to limit the number of accesses to each server, to improve performance, and to reduce the delay in the data transfer by adopting distributed data arrangement.
As a mainly used means for efficiently distributing data to an end user, a cache is disposed on an access network side. Particularly, in content providing service such as Web service, data frequently used by a number of users is stored in a cache server located at a position close to the users than an origin server, and data is distributed to the users from the cache server in place of the origin server. This configuration can reduce a traffic amount in a core network, make network resources effectively used, shorten the response time to the user, and improve the availability of service.
As the information service becomes diverse, it becomes indispensable to identify user information traffic and information service traffic. At present, a switch adapted to a high-order layer, for example, layer 7 switch for switching traffic according to the information in an application layer is widely used. This type of switches are employed to reduce the load of servers. For example, in a system including a plurality of servers corresponding to different services, by distributing traffic to the servers according to the contents of a user request or the state of load on the servers, individual performance of the servers can be improved.
In a network in which a plurality of servers having the same content are located in places apart from each other, means for selecting an optimum server on the basis of the network address of the user to which data is to be distributed, loads on the servers and response time, and sending a request to the selected server is also employed. The server load distributing technique is a control technique of a local traffic in a site, and it is different from a routing control based on a network address. At the present stage, attention is paid to the techniques of reducing traffic and a technique related to a network control at the time of data transfer does not exist.
Due to broadening of a bandwidth of access lines, dramatic increase in memory capacity of storages and, further, spread of mobile communication terminals in recent years, traffic of multimedia data such as a moving image and sound via a network increases and relocation of business data frequently occurs. When large data is used via a network as a network bandwidth is being widened, it is predicted that burst data traffic frequently occurs in places in a network. Traffic tends to increase in the form that streaming data or the like continuously flows in a network bandwidth for predetermined time.
According to a conventional routing in the network layer, since a route on a network is unconditionally determined in a routing table, there is a tendency that traffic is concentrated on a specific route and link source usage is unbalanced. Particularly, in the case where dense traffic occurs in a section on the network, there is the possibility that congestion or a link failure caused by the congestion occurs due to constraints of performances of a route search processing and packet switching processing.
Each router has to distribute large data with short delay and at low loss rate. However, for the above-described reasons, it is difficult for a conventional network system to sufficiently deal with an increase in traffic accompanying distribution of large data.
In a CDN as a technique adapted to distribution of large amount of content, response to a request is improved by adopting a distributed arrangement of servers and caches. However, since the network layer routing protocol is used at the time of data distribution, a problem similar to that of the routing control remains unsolved. To be specific, when dense traffic is concentrated, transfer efficiency deteriorates.
On the other hand, IP-VPN service of combining routing control by traffic engineering with the CDN is in increasing demand and an interest in bandwidth control is growing. In the traffic engineering, however, a function addressing a change in bandwidth usage after setting of a route is not prepared, so that a problem of concentration of processes on a specific line remains unsolved when traffic is dense. This is one of critical problems to be solved in future in a network in which streaming data and real-time communication become the main stream instead of download data. A network node in future needs the function capable of efficiently using a bandwidth in order to distribute large data.